I'm very impressed, Colin.  Just reading through the list of creatures/characters at the end reminds me why I like Donjon so much ("Looks like a real honeybee" as an ability...that is cool).  And that picture of the monkey creature with the beard, what the sam hill?!  Is that a real creature, or photoshopped somehow?  Freaky.

I haven't read through all the text yet, but I think this is a very bang up job, and a spur to other Donjon lovers to do similar things. 

A few points on your "Magic Words" section (page 5):

You said:

Here’s a good guideline: if your spell simply deals damage, it’s not going to work. If your spell calls for a saving throw (PP&T or I&C), that’s fine.

 

I'm not really sure what you mean by this.  Did you mean "If your spell is resisted by a Werewithal plus a resist damage ability, its not going to work"?  I ask because it is my understanding that all spells are resisted by something, nothing just "deals damage".  It could be Werewithal plus a damage resist ability, or Adroitness plus a dodging ability, or Discernment + I&C, or Werewithal + PP&T, or just about anything else the imagination of player/GM can come up with that seems approrpriate.  If I am understanding what you are saying, you would be better off just to say something like:

Spells that reduce a Characters flesh wounds and attributes through a Damage test are simply not possible in the Green, regardless of the magic words used.  Magic just isn't powerful enough to damage someone;  the immortals have stolen much of the power of magic to do direct harm for themselves.

Note that I would certainly still try to use magic to temporarily reduce attributes through facts, as both player and GM.  For example, I have Web as a magic word.  I get 4 successes against the opponents resisted Adroitness plus Dodging ability roll for my "Strands of Iron Strength" spell.  I use one of those successes to state the fact "The strands of iron strength envelop his sword arm" and then use the remaining 3 success to penalize my opponents Adroitness -3 for attacks until he can use facts to clear the gunk off.

You said:

Words that involve mind-control are out, including Charm, Dominate, Hypnotize, Convincing, and similar approaches. It is impossible to dictate the actions of others.

What constitutes "mind-control"?  Some examples:

• I am a famous Khaggi Bug-Tamer and have Insect as a magic word, and am fighting a Swarm of Giant Bees.  Can I use my "Insect Scent Signals" spell to state facts to control the actions of the swarm?
• I am a mad but reclusive Water Folk Hermit with Hallucinatory as a magic word, and some pesky Eya raiders are poking around my cave.  Can I use my "Fevered Visions" spell to state facts to dictate how a character responds to the hallucinations I am causing (i.e. "you attack your buddy Smoking Jaguar because you think he is a vicious Assassin Tree")?
• I am a sinister Eya Sacrificer and have Flesh and Blood as magic words.  Can I use my "Living Puppet" spell to make people's bodies do what I want them to do, regardless of what their minds are telling them?

What I am getting at is that players are incredibly clever in the ways they use the facts that their successes give them.  Any of the above could be defined as "mind-control" or not, depending on the group.  So what did you mean:

• Did you really want to absolutely prevent someone from specifying the actions of another character?  If that is the case, the "Mind control" issue is a red-herring.  Simply leave the last sentence of this section and get rid of the rest, as in:

No spell can dictate the actions of another character.

Personally, I recommend against this, as all of the examples I give above would be prevented and I think they are all cool and seem valid given the setting.
• Did you mean to prevent a certain kind of telepathic/mind reading magic that just doesn't make sense in the setting?  If so, I would add some more fictional content to this section to explain what is prohibited, and why, as you did in the section that immediately follows it about speaking with the dead/gods/etc.  Providing a setting-based reason will help players understand better what it is and isn't reasonable, such as:

Spells that involve direct mind to mind contact, for the purpose of controlling another's mind, altering memories, direct telepathic communication, etc, are not possible; the Green is a very organic place, and the brain is just another organ of the body, a computating hunk of grey flesh.  Mind-to-mind contact make as much sense in the Green as Liver-to-Liver contact.

You said:

Words that are used for the purpose of extending one’s lifespan or returning
others from death are also disallowed.

In general, I think you are better off specify the THINGS magic can't and can do, instead of putting specific words off limits.  For example, is "Death" a valid magic word, based on the sentence above?  Perhaps a better phrasing for this section would be:

Spells that are used for the purpose of extending one’s lifespan or returning
others from death are disallowed.

I'm going to read through the rest of this, because it all looks like a lot of fun.  Good work!